As data communication networks become evermore common place, so-called “home networks” where household appliances and computers in a household are connected to other peripheral equipment using a network so as to enable communication between each item of equipment have become more widespread. Home networks provided convenience and comfort to a user by enabling the data processing functions of each item of equipment to be shared through carrying out communication between network-connected equipment, and exchanging content etc. between equipment etc., and are predicted to become even more widespread in the future.
Universal Plug and Play (UPnP) is well-known as a protocol benefiting from this kind of home network configuration. Universal Plug and Play (UPnP) enables networks to be constructed in a straightforward manner without the need for complex operations, and enables the receiving of services provided by each item of connected equipment for equipment connected to the network without necessitating complex operations or settings. UPnP has the advantages of not being dependent on the OS (operating system) on a device and can easily be added to equipment.
UPnP converts definition files conforming to XML (extensible Markup Language) between connected equipment so that equipment can recognize other equipment. An outline of UPnP processing is as follows.
(1) Addressing processing for acquiring an own-device ID such as an IP address.
(2) Discovery processing of searching for each device on the network, receiving responses from each device, and acquiring information such as device classification, and function contained in the responses.
(3) Service request processing for requesting services at each device based on information acquired in the discovery processing.
Providing and receiving of services appropriate for the equipment connected to the network is then made possible by carrying out the above processing procedure. Equipment newly connected to the network then acquires a device ID using the addressing processing and acquires information regarding other devices connected to the network using the discovery processing, with service requests then being made possible for other equipment based on the acquired information.
For example, in the case of reproducing content such as audio data or image data etc. stored at a server at a client-side device, requests to acquire attribute information for various content information stored in the server such as, for example, compressed information for songs, movie titles, artist names, or data (ATRAC: adaptive transform acoustic coding, MPEG: moving picture experts group, etc.,), or copyright information when required, are sent from the client-side to the server. This attribute information is referred to as metadata or tag information.
The server sends metadata (attribute information relating to content held by the server to the client according to requests from the client. The client then displays content information at a display of a client device in accordance with a prescribed display program based on the metadata acquired from the server. For example, song lists etc. comprised of artist name and title etc. are displayed at the display. The user then confirms or selects reproduction target content based on the displayed information and sends a content transmission request to the server. The server then receives the content request from the client, transmits content to the client from the server according to requests received, and received content is reproduced on the client side.
It is therefore possible for content stored on a server within a home network to be accessed from other equipment connected to the network. For example, it is possible for content to be acquired by equipment implementing UPnP connection having the above straightforward equipment connection configuration. When the content is movie data or music data, if a TV or player etc. is connected as equipment connected to the network, it is possible to watch a mover or listen to music.
Various content such as music or image data etc. is usually transmitted and received between of the items of equipment as various forms of coded data stored in storage units of each item of equipment. For example, in the case of audio data this will be ATRAC3: adaptive transform acoustic coding3, or ATRAC3plus, and in the case of image data, this will be MPEG1: moving picture experts group 1, MPEG2, MPEG4, etc.
However, personal computers, PDAs, or mobile telephones (including PHS terminals) may be used as the client equipment. It is therefore possible that there may be differences in the specifications of the client equipment (display performance, moving picture reproduction performance, audio reproduction performance, etc.) occurring due different equipment being used, or due to a manufacturer or model number being different even when the type of equipment is the same. There may also be differences in the forms of connection to the network for the client equipment (type of line, data transfer speed of line, etc.). Differences therefore appear in content reproduction performance with respective client equipment with regards to what kind of equipment is used as the client equipment, etc.
As a result, in a related server-client system for distributing content, in order to achieve compatibility with various client equipment on the server side, pluralities of the same content in different formats for implementing conversion processing for original content are prepared at a data conversion unit of the server. Content of a format corresponding to the content reproduction performance of the client equipment is then distributed according to content requests from the client side. A method for enabling a client to perform a search in line with file attributes to acquire data is disclosed in, for example, Japanese Patent Laid-open Publication No. 2001-22625 (A method for searching in line with file attributes, and acquire data).
However, when data conversion is executed at the server, the data after conversion has deteriorated compared with the original data. The client then specifies a data specification according to functions possessed by an own-device, and makes a content request to the server. For example, when the client is capable of processing GIF and JPEG image data, image data of one of GIF or JPEG is specified, and a content transmission request is carried out. The server then sends image data that is one of GIF or JPEG to the client in accordance with requests from the client.
The client then reproduces and output content received from the server based on an own-data reproduction program. However, it is not possible on the client-side to make a determination as to whether the reproduced content is content that has undergone data conversion at the server or is original content that has not undergone data conversion. In the case of converted data, the client carries out reproduction of data that has deteriorated after conversion. A situation therefore occurs in reality where the client is forced to reproduce converted data regardless of whether reproduction processing of high quality original data is possible.